1. Field of the Invention
The present invention relates to a process for recording sound images on color photographic light-sensitive materials. More particularly, the present invention is concerned with the formation of one or more optical sound tracks on multi-layer color photographic light-sensitive materials.
2. Description of the Prior Art
In general, methods of recording sound images on color photographic light-sensitive materials used in movies and television are divided into optical recording processes and magnetic recording processes. The present invention is concerned with a method of forming sound tracks suitable for optical recording processes, typically at one edge of the material.
Sounds recorded by optical recording processes on color print films, color reversal films, color reversal print films, and the like used in the field of movies or television are reproduced through the stages of converting the sound signals recorded as a variation in densities or areas into light signals, converting the light signals into electric signals by a light-acceptor, and then converting the electric signals into sound signals. In this reproduction, photoelectric tubes having various spectral properties are used as the light-acceptor. Photoelectric tubes of the "S-1 type" are most widely used and they have a maximum spectral sensitivity at about 800 m.mu. in the infrared region (see, for example, Adrian Cornwell Clyne, Color Cinematography, page 593 (1951)).
On the other hand, in conventional subtractive color photographic light-sensitive materials, the main absorption of dyes produced by coupling of the oxidation products of developing agents such as paraphenylenediamines with color couplers is in the visible region, which does not correspond with the spectral properties of the above described photoelectric tubes. Therefore, the sound output due only to these colored dye images is extremely weak and practically unusable. Thus, in sound reproduction using color photographic light-sensitive materials, a treatment wherein silver or silver sulfide images are formed on the sound track is usually conducted during processing, and the densities of these silver or silver sulfide images in the infrared region are utilized for sound reproduction. In this case, the infrared density (transmission density) is generally from about 1.0 to about 1.6.
The formation of a sound track on color print films can be carried out by processing as described in, for example, Journal of the Society of Motion Picture and Television Engineers, Vol. 61, page 667-701 (1953).
In accordance with this method, color images in the picture image zone and sound images in the sound track area are simultaneously color developed in a color developing bath. In a first fixing bath, unexposed silver halide is removed and then the developed silver produced at development is re-halogenated in a bleaching bath. At the sound developing stage, silver halide only at the sound track area is converted into silver images by selectively coating a viscous sound developer onto the sound track area. In a second fixing bath silver halide in the picture image area is removed by fixing, whereafter dye image are stabilized in a stabilizing bath. The densities in the infrared region are predominantly used in sound reproduction.
As described above, the production of the sound track in color films requires a processing step wherein silver or silver sulfide images are produced. The reason why such a sound track comprising silver or silver sulfide is provided is, as described above, that the spectral properties of photoelectric tubes as are used in sound reproduction have their maximum sensitivity in the infrared region, whereas the colored dyes produced by color development are not dyes of a sufficient density in this wave-length region. A step wherein silver or silver sulfide images are formed in the sound track area is required in addition to a step wherein dye images are formed in the picture image area. A method of forming sound images without using any such special processing stage has been desired by the art.
Recently, as one means of solving the above problem, method has been proposed which comprises incorporating into the silver halide emulsion layers of a color photographic light-sensitive material compounds which markedly reduced the speed of silver bleaching at the bleaching step of color processing or which substantially prevent the silver bleach, or compounds that cause silver bleaching only at the beginning of the silver bleaching step to attain a definite degree of silver bleaching, but thereafter cause substantially no additional silver bleaching. Hereinafter, compounds capable of controlling or interrupting silver bleaching are called "silver bleach inhibitors".
In general, color photographic light-sensitive materials comprise a support and silver halide emulsion layers having different light-sensitive regions superposed on the support. An image-wise exposure followed by color development of such a photographic material provides dye images and silver images. Then, upon bleaching, the silver images are oxidized and then removed from the photographic materials by fixing. Thus, color photographs comprising only dye images are obtained.
The above described color photographic light-sensitive materials have at least one layer containing silver bleach inhibitors capable of forming silver images which cannot be removed by bleaching, and they can provide color photographs having silver images together with color images by conventional color processings. These silver images can advantageously be used as the sound track.
As color photographic light-sensitive materials having at least one layer containing the above described silver bleach inhibitors and capable of forming silver images which cannot be removed by silver bleaching (hereinafter, this layer is referred to as a "sound track forming layer"), there can be mentioned color photographic light-sensitive materials having picture image-forming silver halide emulsion layers and sound image-forming silver halide emulsion layers containing non-diffusible silver bleach inhibitors (for example, non-diffusible thiol compounds) incapable of forming a picture image upon picture image-wise exposure, as described in, for example, U.S. Pat. No. 3,715,208.
Moreover, color photographic light-sensitive materials having picture image-forming silver halide emulsion layers and sound image-forming silver halide emulsion layers containing compounds which do not form a picture image by the picture-imagewise exposure, but which split off non-diffusible silver bleach inhibitor on reacting with oxidation products of developing agents, as described in U.S. Pat. No. 3,705,801, can be used.
Color photographic light-sensitive materials having picture image-forming silver halide emulsion layers and silver halide emulsion layers containing as the silver bleach inhibitor compounds containing at least two oxyethylene groups, as described in U.S. Pat. No. 3,869,287 can also be used.
Color photographic light-sensitive materials having picture image-forming layers and silver halide emulsion layers containing nitrogen-containing heterocyclic compounds containing a thioether bond as the silver bleach inhibitor, as described in U.S. Pat. No. 3,940,271, can further be used.
Color photographic light-sensitive materials having picture image-forming silver halide emulsion layers and sound image-forming silver halide emulsion layers containing nitrogen-containing heterocyclic compounds containing nitrogen atoms which combine with groups containing 11 or more carbon atoms to form quaternary salts as the silver bleach inhibitor, as described in British Pat. No. 1,429,108 can in addition be used.
With any of the above described light-sensitive materials having sound track forming layers, the sound track-forming layers should not have a silver concentration so high that color reproduction is undesirably influenced after conventional picture image-forming exposure followed by conventional processings. That is, the presence of a great deal of silver in color images after conventional picture image-forming exposure followed by conventional processings produces color turbidity, which is harmful to accurate color reproduction.
In order to eliminate the production of silver images in the picture area, which are harmful from the standpoint of color reproduction, British Pat. No. 1,429,108, for example, describes that where the spectral sensitivity of the sound track-forming layer and that of the picture image-forming layer overlap, the former's sensitivity is reduced to not more than one fourth, preferably not more than one sixth, that of the latter's sensitivity. In accordance with this method, silver sound images in the sound track-forming layer which are obtained by picture image-forming exposure followed by conventional processings are formed only at the highest density area. These silver images formed, as a result, intensify black areas of the color picture images, and provide a rather desired effect from the standpoint of color reproduction. On the other hand, sound exposure through a sound original film for producing the optical sound track must be carried out at high illumination intensity as the sensitivities of the sound track-forming layers are low as described above. Therefore, when sound image-forming exposure is conducted, the picture image-forming silver halide emulsion layers of higher sensitivity are excessively exposed to light, thereby forming color sound images together with silver sound images at the sound track area. Since these color sound images are excessively exposed to light they are liable to lack sharpness, which is harmful from the standpoint of sound reproduction.
To remove the above faults, it is preferred that the spectral sensitivity of the sound track-forming layer be separate from that of the picture image-forming silver halide emulsion layers, i.e., it is ideal if the sound track-forming layer is not exposed to light by a common picture image-forming exposure, whereas the picture image-forming silver halide emulsion layer is not exposed to light by the sound image-forming exposure through the sound original film. Conventional subtractive multi-layer color photographic light-sensitive materials are produced by coating a first light-sensitive silver halide emulsion layer which has its sensitivity in the blue region of the spectrum, containing couplers which react with oxidation products of developing agents, thereby forming yellow dyes; a second light-sensitive silver halide emulsion layer which has its sensitivity in the red region of the spectrum, containing couplers which react with oxidation products of developing agents, thereby forming cyan dyes; and a third light-sensitive silver halide emulsion layer which has its sensitivity in the green region of the spectrum, containing couplers which react with oxidation products of developing agents, thereby forming magenta dyes. The formation of color images is carried out using these sensitivities to blue, red, and green of the spectrum. Therefore, if the spectral sensitivity of the optical sound track-forming layer is made distinct from that of the color picture image-forming silver halide emulsion layers and these layers are exposed to rays having different wave lengths, undesired superposition of silver picture images on color picture images and undesired superposition of color picture images on sound images can be prevented. As one such attempt, U.S. Pat. No. 3,737,312 proposes a color photographic light-sensitive material having a silver halide emulsion layer (optical sound track-forming layer) with spectral sensitivity in the spectral wavelength region where the spectral sensitivity of the color picture image-forming layer is lowest. In this case, the spectral wavelength region where the spectral sensitivity of the color picture image-forming layer is lowest is, in the case of conventional subtractive color photographic light-sensitive materials, in the range of about 470 nm to about 480 nm (between the blue region and the green region of the spectrum), and in the range of about 580 nm to about 660 nm (between the green region and the red region of the spectrum). Therefore, by setting the spectral sensitivity of the sound track-forming layer in the range of about 470 nm to about 480 nm or about 580 nm to about 600 nm, and by carrying out sound image-forming exposure with light of such a wave length, undesired superposition of picture silver images on color picture images is avoided. However, since light having a wave length of from about 580 nm to about 600 nm is used as a safety light for conventional subtractive color print rilms, if the spectral sensitivity of the sound track-forming layer is set in this range, the sound track-forming layer would be subjects to fogging by light of this wavelength region, used as safety light. For this reason, it is undesired that the spectral sensitivity of the sound track-forming layer be set in the range of about 580 nm to about 600 nm.
U.S. Pat. No. 3,737,312 describes that it is desired to set the spectral sensitivity of the sound track-forming layer to between about 470 nm and about 480 nm. However, as a matter of fact, in the region of about 470 nm to about 480 nm where the spectral sensitivity of the picture image-forming silver halide emulsion layers is lowest, the picture image-forming silver halide emulsion layers have relatively high sensitivity. Therefore, setting of the spectral sensitivity of the sound track-forming layer in this range inevitably causes undesired super-position of silver picture images on the color picture images, and undesired superposition of the color sound images on the silver sound images.
As a second method of eliminating the undesired superposition of silver images on color images and the undesired superposition of color sound images on silver sound images, it was considered to set the spectral sensitivity of the sound track-forming layer in the infrared region. The maximum spectral sensitivity of the sound track-forming layer to achieve the above object must be at a longer wave length region, i.e., at least 750 nm. However, spectral sensitizers capable of providing spectral sensitivity in the infrared region are generally unstable, and, moreover, light-sensitive materials subjected to spectral sensitization by the use of these spectral sensitizing dyes are unstable and practically unusable. Furthermore, exposure of the sound track-forming layer is naturally carried out using infrared light, and the selection of filters for obtaining such light is generally limited.
As a third method of eliminating the undesired superposition of silver picture images on color picture images and the undesired superposition of color sound images on silver sound images, it was considered to set the spectral sensitivity of the sound track-forming layer in the ultraviolet region. In general, the light-sensitive region of a light-sensitive silver halide emulsion itself ranges from the ultraviolet region to near 500 nm in the visible region. However, since binders for silver halide particles, generally gelatin, absorb light at the shorter wavelength side of the ultraviolet region, a light-sensitive silver halide emulsion is rarely sensitive at wave lengths shorter than 300 nm. Thus, undesired superposition of silver picture images on color picture images could be prevented by setting the spectral sensitivity of the sound track-forming layer at the spectral sensitivity region of the silver halide emulsion itself, by setting the wave length of light used to sound image-wise expose the sound track-forming layer to wave lengths shorter than about 400 nm, and by setting the wave length of light used to picture image-wise expose the color picture image-forming silver halide emulsion layers to wave lengths longer than about 400 nm, i.e., the visible region. Moreover, filters for obtaining these wave lengths are easily available. In more detail, the picture image-forming silver halide emulsion layers are initially exposed picture image-wise to light by the use of an ultraviolet ray absorbing filter (capable of absorbing rays having wave lengths shorter than about 400 nm) and the sound track-forming layer is then exposed sound image-wise to light using a visible ray absorbing filter (capable of absorbing rays having wave lengths longer than about 400 nm) from the sound original. In this case, however, since the picture image-forming silver halide emulsion layers also have sensitivity at wave lengths shorter than about 400 nm, when the sound track-forming layer is exposed to light the picture image-forming silver halide emulsion layer is simultaneously exposed to light, thereby producing an undesired superposition of color sound images on the silver sound images. In general, at wave lengths shorter than about 400 nm, the sensitivity of the blue light-sensitive silver halide emulsion layer containing yellow dye-forming couplers is highest of the color image-forming layers, and thus undesired superposition of color sound images on the silver sound images is most remarkable at yellow image areas.
The prevention of the undesired superposition of the color sound images on the silver sound images is achieved by interposing a layer containing an ultraviolet ray absorbing material between the support and the sound track-forming layer, i.e., when the sound track-forming layer is sound image-wise exposed to light using rays of wave lengths shorter than about 400 nm, latent images are formed in silver halide grains of the sound track-forming layer. Further, due to the action of the ultraviolet ray absorbing material, no latent image is formed in silver halide grains of the picture image-forming layer. Therefore, undesired superposition of the color sound images on the silver sound images produced by processing multi-layer color photographic light-sensitive materials carrying a sound track-forming layer can be eliminated.
On the other hand, exposure to form the color picture images using rays having wave lengths longer than about 400 nm as described above, i.e., to visible rays, reduces developable latent images formed in the silver halide emulsion of the sound track-forming layer, and thus makes it possible to reduce superposition of silver picture images on the color picture image section.
Since the above mentioned multi-layer color photographic light sensitive material carrying a sound track-forming layer has a layer in addition to the conventional picture image-forming layer, the former light-sensitive material has an increased total coating amount of silver compared with the latter light-sensitive material. The increased total coating amount of silver leads not only to the increased cost of production of the light sensitive material, but also to the decreased sharpnesss of picture images or sound images when a multi-layer color photographic light-sensitive material having a sound track-forming layer is used. That is, when a sound track-forming layer is coated as an outermost layer far from the support, the sharpness of picture images decreases by the irradiation due to the light scattering at the surface of silver halide grains in a sound track-forming layer. On the other hand, when a sound track-forming layer is coated as a layer adjacent to the support, the sound reproduction is insufficient due to decreased sharpness of sound images, though the sharpness of picture images remains unchangeable compared with a conventional multilayer color photographic light-sensitive material. To avoid the above disadvantages in a multi-layer light-sensitive silver halide material carrying a sound track-forming layer, it is preferable to decrease the coating amounts of silver in a sound track-forming layer. In order to decrease the coating amounts of silver in a sound track-forming layer, Japanese Pat. (OPI) No. 77334/1976 describes that the sound track-forming layer contains a silver bleach inhibitor and a heterocyclic thione compound incapable to enolize. U.S. Pat. No. 3,705,801 describes that a silver bleach inhibitor releasing coupler (BIR coupler) which reacts with a color developing agent to form a dye having a relatively longer wavelength absorption maximum, while a silver bleach inhibitor is released, is able to reduce the coating amount of silver in the sound track-forming layer. British Pat. No. 1,429,108 describes that a bleach inhibitor containing a heterocyclic nitrogen atom and a coupler capable of reacting with an oxidation product of a color developing agent can be advantageously used to form a dye whose absorption maximum is at a wavelength longer than 725 nm, so that the coating amount of silver in the sound track forming layer can be reduced.